Back Examination : Straight Leg Raising Test

From Patient.co.uk

Straight leg raising:

• Passively flex thigh with extended leg while patient is supine. Dorsiflexion of foot helps to elicit pain.
  Stop when the patient complains of back or leg pain (hamstring tightness is not relevant). The test is negative if there is no pain. Paraesthesiae or pain in root distribution is very significant, indicating nerve root irritation.
• Lasegue's sign is positive if pain is felt when the leg is raised to 45 degrees or less.
• A positive result on the same side as the pain is said to be about 80% sensitive but only 40% specific; a positive result with the unaffected leg is said to be only 25% sensitive but 75% specific.
• Back pain suggests but is not indicative of a central disc prolapse, and leg pain suggests a lateral protrusion. Pain must be below the knee if the roots of the sciatic nerve are involved.
• Lower the leg until pain disappears and then dorsiflex the foot. This increases tension on the nerve roots, aggravating any pain or paraesthesiae (positive sciatic stretch test).
• Bowstring test: once the level of pain has been reached, flex the knee slightly and apply firm pressure with the thumb in the popliteal fossa over the stretched tibial nerve. Radiating pain and paraesthesiae suggest nerve root irritation.